Topic 3

Question 1

Describe the nucleus

Answer 1

A large organelle surrounded by a nuclear envelope which contains many pores.
The nucleus contains chromatin (DNA and proteins) and a nucleolus.

Question 2

What is the function of the nucleus?

Answer 2

The nucleus controls the cell’s activities by controlling transcription of DNA.
DNA contains instructions to make proteins.
The pores allow substances to move between the nucleus and the cytoplasm.
The nucleus makes ribosomes.

Question 3

Describe a lysosome

Answer 3

A round organelle surrounded by a membrane with no clear internal structure.

Question 4

What is the function of a lysosome?

Answer 4

Contains digestive enzymes.
This are kept separate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or to break down worn out components of the cell.

Question 5

Describe a ribosome

Answer 5

A very small organelle that either freely floats in the cytoplasm or is attached to the rough endoplasmic reticulum.
It’s made up of proteins and RNA.
It has no membrane

Question 6

What is the function of the ribosome?

Answer 6

The site where proteins are made

Question 7

Describe the Rough Endoplasmic Reticulum

Answer 7

A system of membranes enclosing a fluid-filled space.

The surface is covered with ribosomes.

Question 8

What is the function of the Rough Endoplasmic Reticulum?

Answer 8

Folds and processes proteins that have been made in the ribosomes.

Question 9

Describe the Smooth Endoplasmic Reticulum

Answer 9

Similar to the RER but with no ribosomes

Question 10

What is the function of the Smooth Endoplamsic Reticulum?

Answer 10

Synthesises and processes lipids

Question 11

Describes the Golgi Apparatus

Answer 11

A group of fluid-filled , membrane bound, flattened sacs.

Vesicles are often seen are the edges of the sacs.

Question 12

What is the function of the Golgi Apparatus?

Answer 12

It processes and packages new lipids and proteins.

It also makes lysosomes.

Question 13

Describe the mitochondrion

Answer 13

Usually oval-shaped.
Double membrane - inner is folded to form cristae.
Inside is the matrix which contains enzymes involved in respiration.

Question 14

What is the function of the mitochondrion?

Answer 14

The site of aerobic respiration, where ATP is produced.

They’re found in large numbers in cells that are very active and require lots of energy.

Question 15

Describe a centriole

Answer 15

Small, hollow cylinders, made of microtubules.

Found in animal cells but only some plant cells.

Question 16

What is the function of the centriole?

Answer 16

Involved in the separation of chromosomes during cell division.

Question 17

Describe how proteins leave the cell.

Answer 17

1) Made at ribosomes
2) Ribosomes on the RER make proteins that are excreted or attached to the cell membrane. Free ribosomes in the cytoplasm make proteins that stay in the cytoplasm
3) New proteins made at the RER are folded and processed in the RER
4) They’re then transported from the RER to the Golgi apparatus in vesicles
5) At the golgi apparatus the proteins undergo further processing.
6) The proteins enter more vesicles to be transported around the cell.

Question 18

What organelles can be found in Eukaryotic cells?

Answer 18

Nucleus
Lysosome
Ribosome
RER
SER
Golgi apparatus
Mitochondrion
Centriole

Question 19

What organelles can be found in Prokaryotic cells?

Answer 19

Pili
Mesosomes
Plasmids
Flagellum

Question 20

Describe the cytoplasm in a prokaryotic cell.

Answer 20

Contains no membrane-bound organelles.

Has ribosomes but they’re smaller

Question 21

What are Pili?

Answer 21

Short hair-like structures.

Help prokaryotic cells stick together

Question 22

What are Flagellum?

Answer 22

Long hair-like structure that rotates to make cell move.

Not all prokaryotic cells have them.

Question 23

What are mesosomes?

Answer 23

Inward folds in the plasma membrane.
Scientists are still debating what their function is.
Some believe they play a role in cellular processes others they’re artefacts that are proceduced when the cells are being prepared for viewing with an EM

Question 24

Describe a light microscope.

Answer 24

• Use light to form an image
• Maximum resolution of 0.2 micrometers
• Can’t see ribosomes, endoplasmic reticulum or lysosomes

Question 25

Describe an electron microscope.

Answer 25

• Use electrons to form an image
• Higher resolution than light microscopes
• Maximum resolution of 0.0002 micrometers
• Two types: Transmission or Scanning

Question 26

Describe transmission electron microscopes (TEM)

Answer 26

• Use electromagnets to focus beam of electrons, which is transmitted through specimen
• Denser parts absorb more electrons which make them appear darker
• High resolution
• Can see internal structure of organelles
• Only used on thin specimans

Question 27

Describe scanning electron microscopes (SEM)

Answer 27

• Scan a beam of electrons across specimen, knocks off electrons from specimen, these are gathered in a cathode ray tube to form an image
• Images show surface so can be 3D
• Can be used on thick specimens
• Lower resolution then TEMs

Question 28

What are similar cells organised into?

Answer 28

Tissue

Question 29

Name and describe 4 examples of tissue

Answer 29

1) Squamous
- single layer of cells lining a surface

2) Ciliated epithelium
- layer of cells covered in cilia
- found on surfaces where things need to be moved

3) Xylem
- transports water
- supports the plant
- contains xylem vessel cells and parenchyma cells

4) Cartilage
- connective tissue found in joints
- shapes and supports ears, nose and windpipes